Burst Activity of SGR 1806-20 in the hard X-rays

ATel #324; S. Molkov (IKI, Moscow), P. Ubertini (IASF, Roma), C. Jorgensen (DSRI, Copenhagen), C. Winkler (ESA/ESTEC Noordwijk), N. Gehrels (GSFC, NASA)
on 25 Aug 2004; 16:12 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Sergei Molkov (molkov@hea.iki.rssi.ru)

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During one of the regular Galactic Plan Scan performed by the High energy INTEGRAL satellite on 20-21 August, 2004 the Soft Gamma Ray Repeater SGR 1806-20 was in the field of view of the IBIS telescope during ~10 ks. Seven bursts were detected by the ISGRI/IBIS low energy detection plane from the source during this period in the energy band 18-70 keV. This frequency of bursts generation confirms that the source now stays in the active phase (ATEL #313).

The duration of the bursts varied from 30 ms to 240 ms (see the table below). The bursts profile have a complex structure. Two bursts were detected also by the JEM-X telescope in the energy band 3-20 keV. But the JEM-X fluxes are very weak and an accurate flux determination is pending.

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N |    T_start   | Dur. | Sign. | Mean FLUX, 18-70 keV | JEM-X
       (UT)        (ms)          (10^{-7} erg/s/cm2)
1   21T02:30:46.0   50     5.8            2.3             no
2   21T02:37:53.0   50     6.7            3.5             no
3   21T02:37:53.2  240    27.9            8.4             no
4   21T02:47:46.6   30     3.6            2.0             no
5   21T03:15:40.2  100    11.2            2.0            yes
6   21T03:38:26.7  190    27.6            7.4            yes
7   21T04:49:32.3  110    13.2            8.2             no